The present invention relates to a method of manufacturing a semiconductor device wherein a lower metallization layer, an interlayer insulating film, and an upper metallization layer are formed sequentially on a semiconductor substrate. More particularly, it relates to the technology for reducing the relative dielectric constant of the interlayer insulating film.
In the formation of an interlayer insulating film which is low in relative dielectric constant, there have conventionally been known: (1) a method wherein an oxide film doped with fluorine (SiOF) is formed by plasma CVD; (2) a method wherein a TEOS derivative having an organic group as a substituent is hydrolyzed and condensed by dehydration to prepare a silanol sol, which is applied onto a semiconductor substrate and thermally treated to form a SOG film by a sol-gel process; (3) a method wherein a solution of a siloxane polymer is applied onto a semiconductor substrate and thermally treated to form an interlayer insulating film; and (4) a method wherein a solution of an organic polymer is applied onto a semiconductor substrate and thermally treated to form an interlayer insulating film.
In the first method of forming the interlayer insulating film from a solution of a fluorinated silica sol, the relative dielectric constant of the interlayer insulating film can be reduced to about 3.0 by increasing the content of fluorine. When the content of fluorine is increased, however, the moisture absorbency of the interlayer insulating film is extremely increased, so that a minimum relative dielectric constant that can be used in practice is about 3.5.
The second method of forming the interlayer insulating film from the solution of an organic silica sol presents the problems that the relative dielectric constant of the resulting interlayer insulating film is 3 or more, which is comparatively high, and that the interlayer insulating film is easily decomposed by an oxygen plasma since silicon-organic group bonds are evenly distributed in the film on a molecular level, which may cause side etching in forming a pattern by dry etching or degassing due to decomposition, resulting in adverse effects on the production yield of the device including the occurrence of a crack and increased contact resistance.
In the third method of forming the interlayer insulating film from the solution of a siloxane polymer, the relative dielectric constant of the interlayer insulating film is about 2.5, which is lower than the relative dielectric constant of the interlayer insulating film formed from the solution of a fluorinated silica sol. However, since silicon-organic group bonds are evenly distributed in the film on a molecular level, the interlayer insulating film is easily decomposed by an oxygen plasma, which may cause side etching in forming a pattern by dry etching or degassing due to decomposition, resulting in adverse effects on the production yield of the device including the occurrence of a crack and increased contact resistance.
Although the fourth method of forming the interlayer insulating film from the solution of an organic polymer is advantageous in that the relative dielectric constant of the interlayer insulating film is as low as 2, it has poor compatibility with the semiconductor manufacturing process owing to the problems that the strength of the interlayer insulating film is low because of its low resistance to oxygen plasma and that the heat resistance of the interlayer insulating film is low because of its low glass transition temperature.